gritty ballscrews

[Voicecoil]

Just recieved a package from Fred at BST with various ballscrews for my first build, nice smell of machine oil in the flat now. Giving them a twiddle it was immediately noticeable that a couple of them run a bit rough, like they've got swarf or grit in them, the others were fine - maybe not as good as Japanese/European parts I've felt before, but quite acceptable. Before I go and moan at Fred, has anyone else had product like this please? or do I need to clean them, and if so how? Thanks

[routercnc]

Mine ran OK from Fred so either he put ball bearings that were slightly too large or there is grit in there. My experience is that they don’t clean them so that is possible although I’ve not had one which felt gritty.
Fred is usually very helpful so I would mention it to him as I’m sure he would appreciate the feedback and he may offer a few pounds back for the time you will spend taking them apart and cleaning them. Unless you think they are damaged I would spend a bit of time getting to know how they work inside.

There are lots of videos showing how it is done. Make sure when you remove the nut from the screw you catch all the ball bearings which fall out. There are also return guides (orange plastic) which you can also remove but note how they go back.

I don’t have a recommendation for what cleaning fluid to use, some kind of mild degreaser on a cloth.

To refill the ballscrew tracks put a dot of grease on the end of a small implement and use it to hold the ball in place whilst you lower it into the track inside the nut. Use more grease to hold it as required. Repeat until full then carefully insert the keeper tube to hold the balls in place then screw it back into the ballscrew ensuring it is the right way around! It’s doable but fiddly.

Here is my video showing it around 6:00 mins in:
https://youtu.be/yJBE-fxVh8Y

[Voicecoil]

Thanks for the advice and the link to the video; I don't think it's oversized balls as the roughness it intermittent, sometime you can do a turn or 2 OK, then suddenly it graunches and feels dog rough. Also looking at my hands after handling them I see tiny flakes of swarf which points to bits getting into the nuts. Hopefully as I've caught it before running them with motors there won't be any damage, but I'll take a close look at the screw for signs of scratching. Cleaning and repacking looks like a job for a long winters evening, though with the amount I have on at the mo. I could do without it!

[Voicecoil]

So I ran one of the shorter screws through a piece of tissue paper and sure enough there's little flakes of swarf amongst the grease:
25374
Whilst doing this I also noticed that the depth of the residual thread where these 1204 screws had been machined down to 10mm was different one one side to the other:
25375
25376
This says to me that the end machining is off centre, not so good :disillusionment: ......email on it's way to Fred, just hope he has time to sort something before Chinese New Year.

[routercnc]

For info I can't open the attachments. If I hover over them it shows no views so suspect I am not alone.

The graunchiness might be a missing ball, and/or not smoothly going round the plastic ball return track. Ask Fred how many balls there should be in there (mine are 1605 so different to yours).

[AndyGuid]

Yep, I can't access the attachments either.

Get message "Invalid Attachment specified. If you followed a valid link, please notify the administrator"

[Voicecoil]

I don't know what happened to the pics, they were there when I checked the post. I've put them up again, take a peek before they disappear again!

[Voicecoil]

Well, I got a very apologetic email back from Fred, apparently they were rather rushed getting stuff out before Chinese New Year. He's suggested removing the seals and flushing through, apparently this works a lot of the time and is obviously easier than complete dis-assembly.

[phill05]

apparently this works a lot of the time and is obviously easier than complete dis-assembly.

An hour or two spent stripping down, clean properly, and repack would in the long run save you some pain in the future.

Phill

[Voicecoil]

I'm going to try the flushing thing, I know what they should feel like when put together properly and if they don't meet that it'll be a complete strip down :-( . If nothing else, cleaning out some of the crap will make winding the nuts down to get the balls out less graunchy.

BTW, what would be the recommended oil/grease to use when re-assembling?

[AndyUK]

Hows things going with these screws? Had any luck?

If you're still looking for oil/grease recommendations, Lee gave me a great reply recently - the short version being lithium based grease - if you look at the HIWIN greasing guide, you'll also see EP1 mentioned.

http://www.mycncuk.com/threads/11552-AndyUK-s-Build-1-2x1-0m-Gantry?goto=newpost

[Voicecoil]

Yes, Fred has been good to his word and sorted me out with some replacement bits including completely replacing the 1204 screws which had the slightly wonky end machining - you can't fault the guy's service, 10/10. Regarding the grease, looking at the specs Hiwin recommend, I've realised that I already have something that should do - Mobil 1, which I bought for re-packing the struts on the car.

[Voicecoil]

Whilst pondering ways to make a linear motion assembly thinner I pulled out one of these old ballscrews to look at, I'm the kind of guy that thinks much better with something physical in my hands. Whilst idly twiddling it and looking down the end of the nut I noticed there was a definite gap in the line of balls if you held it horizontally and rotated the screw, you could hear the balls tipping over the crown of the screw as they made their way down the other side, sometimes accompanied by a sudden roughness is the rotation force. If you held the screw upright this didn't seem to happen, presumably gravity was sorting things out. This made me think, shouldn't there be a more or less continual line of balls??? could this be why they still felt rough after quite a bit of cleaning out of swarf?? Any advice from linear motion experts would be very welcome.